I have sworn by OxyClean (original powdered form) for YEARS! I have white carpet in my house and we've lived there over 8 years. I also have an area rug in the dining room (hardwoods under) that has an off white background. All my carpets have had MAJOR spills and accidents (lots of red wine, various food, and other things I don't need to go into). I keep a tub of the OxyClean in my laundry room (just off the kitchen); depending on the size of the problem, I take OxyClean, mix it with hot water in the appropriate container, scoop it on and blot it off. It NEVER fails me!

We also have a Bissel scrubber we use every couple of years for all the carpet.